Overall Summary For the past 15 years our Program Project CA87497 has been highly productive and interactive. The future goals of this program are to study the context-dependent tumor suppressive roles of wild-type p53, and to elucidate how cancer related mutant forms of p53 promote oncogenesis. We will investigate newly discovered pathways in which wild-type and mutant p53 proteins operate and their respective roles in regulating the epigenome and characterize new transcriptional targets of p53. In addition to the current members, Drs Carol Prives, Arnold Levine, Scott Lowe and Carlos Cordon-Cardo, we have brought in Drs Brent Stockwell and John Petrini who each contribute new and exciting directions that interface with the existing projects. Our approaches include cell biology, chemical biology, biochemistry, proteomics, microscopy, bioinformatics, functional genomics, mouse modeling and human and mouse pathology. Our research is highly translational and relevant to human disease, focusing on breast cancer, liver cancer and lymphoma. Project 1 (Prives) will investigate mutant p53 gain of function activities employing cell-based assays, gene expression profiling and proteomics. Project 1 will elucidate how and why mutant p53 stimulates the mevalonate pathway, while wild- type p53 represses this same pathway, and will obtain mechanistic information as to how mutant p53 facilitates nucleosome remodeling. Project 2 (Stockwell), will define mechanisms that govern p53 regulation of ferroptosis, which his group discovered. Planned work will define how the p53 target p21 acts in a negative feedback loop to restrain ferroptosis, how p53 regulates ferroptosis through its effects on the mevalonate pathway, and how nutrient deficiency regulates p53 and its impact on ferroptosis. Project 3 (Petrini) will quantify and determine the location of p53-dependent epigenetic changes induced by oncogene activation in mammary epithelium and will determine whether this novel pathway is operative in hematopoietic cells, and assess its importance for suppression of lymphomagenesis and myeloid leukemia. Project 4 (Lowe) uses advanced genetic and genomic tools together with novel genetically-engineered mouse models to explore mechanisms of p53-mediated tumor suppression in different tissue and genetic contexts, and the role of novel p53 mutants on tumor initiation and progression in vivo. It will also explore the role of ferroptosis in tumor suppression and how deregulation of p53-mediated gene repression programs including the mevalonate pathway contributes to tumor maintenance. The planned research will rely extensively on three cores: Core A (Prives), that will administratively support all interactions within the program, the Bioinformatics Core B (Levine) that will provide crucial computational support for each project in order to aid in the discovery of genes and pathways regulated by mutant and wild-type p53 in different contexts. Core B will test new hypotheses and identify new modulators of wild-type and mutant p53. The Molecular Systems Pathology Core C (Cordon-Cardo) will provide critical information regarding human tumors including new molecular biomarkers derived from mevalonate and ferroptotic pathways. Core C will also quantify heterochromatic marks and will study biomarkers of mutant p53, stem cells, and new repression targets in liver and lymphoma samples.